Varnish removing hydraulic fluids



United States Patent 3,090,758 VARNISH REMOVING HYBRAULIC FLUIDS Thoririld F. Lonstrup and Thomas J. Matehett, Sarnia,

Lamhton, Ontario, and James H. Norton, Corunna,

Lamhton, Untario, Canada, assignors to Essa Research and Engineering Company, a corporation of Delaware No Drawing. Filed Jan. 30, 1961, Ser. No. 85,485

1 Claim. (Cl. 252-77) This invention relates to varnish removal from the surfaces of hydraulically operated machinery. In particular, it relates to hydraulic fluid compositions having improved varnish removing properties.

Many machines are hydraulically operated, that is, hydraulic systems are used for control and transmission of power. These include such equipment as die casting machines, hydraulic presses, forging presses, extrusion presses, door checks, aircraft hydraulic systems, servo controls and the like. The hydraulic fluids used in such machinery are generally low viscosity petroleum based, high grade oils which are fortified against oxidation, wear, rust, emulsion, and foaming. They also include non-flammable type hydraulic fluids known as fire resistant hydraulic fluids such as alkyl and aryl phosphates, polyethylene glycols, water-in-oil emulsions, water-glycol blends and the like. A problem in the use of hydraulic fluids is that even the most highly oxidation resistant ones tend to oxidize when used for extended periods. This oxidation results in severe varnish deposits throughout the interior of a hydraulic system. Such deposits cause sticking of essential parts of the hydraulic system such as valves, pistons, pump vanes, pump rings, and the like, and especially in the control mechanisms. The sticking causes erratic performance of the equipment. In order to remove this varnish and eliminate the erratic performance caused by the sticking, the present practice is to interrupt the operation of the machinery, disassemble the machinery and treat the affected parts with a suitable varnish removing solvent. Alternatively, the hydraulic fluid can be drained and a solvent can be run through the machinery in order to clear the affected parts of the undesirable varnish. Both techniques of varnish removing are unsatisfactory in that the operation of the hydraulic machinery must be interrupted in order to remove the varnish and labor must be expended in order to disassemble the machinery or run suitable solvents through the apparatus.

This invention resides in the discovery that certain compounds can be added to hydraulic fluids to impart a high order of varnish removing ability to the fluid. This feature is extremely desirable in that it eliminates the time and work entailed in the varnish removing practices now employed. There are two primary features of the invention. The first is that a suitable hydraulic fluid composition may be employed initially in the hydraulic system so that varnish deposits are prevented. The second feature is in the use of a hydraulic fluid which has the dual role of a flushing oil towards varnish and sludge. In the latter feature a seriously, varnish-encrusted machine is drained of its hydraulic fluid which is replaced with the flushing type fluid of the invention. This removes the varnish while permitting the use of the hydraulic machinery in its regular tasks.

The hydraulic fluid composition suitable for the flushing oil feature of the invention comprises a hydraulic fluid with from 0.01 to 1.0 e.g. 0.1 to 0.5 wt. percent based on the weight of the fluid of an oil soluble varnish removing additive mixture incorporated therein. The varnish removing additive comprises from 1 to 5, e.g. 1 to 3, molar proportions of a C to C e.g. C to C monoalkyl amine, and one molar proportion of a monoalkylated phenol-alkylene oxide condensation product. The monoalkyl phenol portion of the condensation product has a saturated unsubstituted alkyl group of from 6 to 12 carbon atoms. The alkylene oxide portion of the condensation product has from 2 to 6 carbon atoms per molecule. From 2 to 6 moles of the alkylene oxide are condensed with each mole of the alkyl phenol. The two components of the additive mixture exhibit synergistic activity and are exceptionally effective varnish removers in that they remove large quantities of varnish within a relatively short span of time.

The feature of the invention, wherein the hydraulic fluid has an inherent varnish removing ability comprises a hydraulic fluid with from 0.01 to 1.0, e.g. 0.1 to 0.3 wt. percent based on the weight of the fluid of a C to C e.g. C to C monoalkyl amine. Many other surfactants were evaluated. None exhibited the satisfactory properties of either the additive mixture or the amine additive alone with respect to combining both superior varnish removal properties and lack of foam.

Other additives may be added to the varnish removing hydraulic compositions to enhance other properties of the fluid. These additives can be rust inhibitors, oxidation inhibitors, antiwear agents, antifoam demulsifiers, pour point depressants, viscosity index improvers, o-iliness agents and the like.

The invention will be further illustrated by the following examples. All additive weight percentages are based on the Weight of the hydraulic fluids.

EXAMPLE 1 The following compositions were. prepared from a hydraulic oil having a Dean and Davis viscosity index of 97 and a viscosity of SSU at 100 P. which was derived from a Western Canadian crude by vacuum distillation, followed by phenol extraction, solvent dewaxing and hydrogenation. Four portions of this oil were utilized. To the first portion was added 0.1 wt. percent of a C monoalkylated phenol/ ethylene oxide condensation product having 4 molecules of ethylene oxide per molecule of phenol and having the formula:

To the second portion was added 0.2 wt. percent of a mixture comprising 6 wt. percent of a C monoalkyl amine and 94 wt. percent of a C monoalkyl amine. To the third portion was added 0.1 wt. percent of the alkylated phenol/oxide condensation product and 0.2 wt. percent of the same amine mixture. The fourth portion of oil was used as a control and labelled composition A. The compositions with additives were labelled compositions B, C and D respectively. These compositions were then tested as follows:

A brightly polished weighed steel rod /2" in diameter and 2.6" long was coated with a layer of varnish derived by oxidizing a lubricating oil. The steel rod with varnish was then immersed in the composition tested. The composition was kept at a temperature of F. and a motor driven stirrer was used to circulate the oil. After a specified length of time, the steel rod was immersed in petroleum naphtha to remove the oil, dried and the quantity of varnish removed was determined by weighing. The result is expressed as percent removed of the original amount.

The following table summarizes the results of the above tests:

As can be seen from the above table, after one hour oils containing only the amine and only the condensation product removed more varnish than the base oil control (composition A). However, composition D having the combination of two additives is appreciably better than the base oil or the compositions (B and C) having only a single additive.

EXAMPLE 2 Nine compositions labelled E to M were prepared. These compositions were tested in the same type of test as described in Example "1 except that the time was 19 hours. The base oil (control) used was also the same as that of Example 1. The formulations of the compositions and the test results are summarized in the following table.

1 Range for five tests.

As can be seen from the above table a wide variety of surface'active materials was evaluated in order to ascertain their efiectiveness with respect to varnish removal combined with lack of foaming. Some of the surfactants were effective varnish removers but this characteristic was accompanied by foaming. Others did not foam but were not very effective varnish removers. The most effective varnish remover and non-foamer was Composition E, containing 0.2 Wt. percent of the alkyl amine mixture of Example 1. Thus, it is clear that, compared with a variety of other surfactants, only the specific aliphatic amine having the specific chain length is effective in this test.

EXAMPLE 3 The varnish removing properties of a nonflammable hydraulic fluid containing the additives of Example 1 were also evaluated in the same type of test. The nonflammable fluid was composed of 54.0 wt. percent of mineral oil having a viscosity at of SSU and a viscosity index of 70, 40.0 wt. percent of Sarnia, Ontario, Canada, tap water, 2.7 wt. percent of polyoxyethy-lene sorbitan monooleate, 2.7 wt. percent of isopropanol and 0.6 wt. percent of nonyl phenol plus 0.0005 wt. percent.

based on the weight of the preceding components of a methyl silicon fluid having a viscosity of 350 cs. at 75 F. Compositions N and 0 were prepared from the nonflammable hydraulic fluid. Composition N was the nonfl-ammable hydraulic fluid per se. Composition 0 was the non-flammable fluid containing 0.2 wt. percent of the amine additive of Example 1 plus 0.1 wt. percent of the alkylated phenol-ethylene oxide product referred to in Example 1. The compositions were evaluated in the Example 1 test after 19 hours. The results are summarized in the following table.

0. additives-l-N 1 Range of 5 tests. 2 Average of 2 tests.

As can be seen from the above table, the non-flammable fluid itself has a relatively good varnish removing ability as compared to straight mineral oil, i.e., the control of Example 2. However, the composition containing the additives is substantially better in this essential characteristic.

What is claimed is: p

A hydraulic oil capable of removing varnish deposits from the surfaces of hydraulically operated machinery, comprising a major amount of a mineral oil, about 0.2 wt. percent of C -C monoalkyl amine and about 0.1 Wt. percent of the condensation product of a molar proportion of mono-nonyl phenol and about 4 molar proportions of ethylene oxide. 7

References Cited in the file of this patent UNITED STATES PATENTS 

